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Roadmap n The topic: interfaces between the nervous system and electronic devices n Why? n What could they do for us? n Do we really need that? n How? n What problems do we have to solve? n What techniques have been tried? n What will we do next?

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n Control artificial limbs and organs (or anything else that can be run by a computer…) Nerve Chips: Why? n What could we do if we could tap into neural signals? Y Matsuoka, 2001 P Heiduschka and S Thanos, 1998 n Replace missing sensory data n Route them around dead or damaged tissue n But even better yet….

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What Do We Have to Do? n Get our interface into the body n Keep the body from attacking and rejecting the chip n Get close to the target nerve cells n Transmit electrical current to the targets n Don’t transmit current to non-target cells n Don’t harm the nerve with too much current n Record signals from the targets n Try to separate out the voices of single cells n Do all this to thousands of cells at the same time n Adapt to the body changing over time

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How Do We Do It? (1) Nerve Cuff n Flexible cuff wrapped around a whole nerve n Mechanically stable n Not very selective n Causes muscle fatigue n Can’t use in brain n Still a popular method because it’s simple and stable P Heiduschka and S Thanos, 1998

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How Do We Do It? (2) Sieve Electrode n Axons of a cut nerve regenerate through holes in silicon chip n Lets us talk to individual axons n We either have to wait for a nerve to get cut or cut it ourselves n Not in the clinic yet, but soon… L Wallman et al., 1999

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How Do We Do It? (3) Microelectrode Array n Array of tiny conducting spikes n Can stick it anywhere in the nervous system n Can’t be sure every spike will hit a cell n Can damage tissue n Some clinical trials ongoing n Versions of this let you do some semi-cool things with animals PJ Rousche and RA Normann, 1998

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What’s Still Missing? n All of these still use pretty big currents n Hurts the cells, rapidly fatigues the muscles if stimulating them directly n Need to be talking to a lot more cells to get true biological precision and resolution n Only one (sieve electrode) is really specific for individual cells n Can always use more mechanical stability and biocompatibility

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The Next Step? n Make a chip that has living neurons built into it n Use those living cells as your connection to the patient n Nothing is better at talking to neurons than other neurons…

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How Do We Get There? n Nanotechnology – design of new “impossible” materials n Electrode coatings that contain brain molecules, “trick” cells into acting like electrode is part of brain n Polymer chains that can enter the cell n Conductive polymer chains that place your electrode inside a cell without hurting it n Components that “self-assemble” through chemical forces n Other crazy stuff I haven’t thought of yet